Transport of particulate solids during the production of fluids from a wellbore has long presented a problem in the recovery of fluid mineral values from subterranean formations. Such transported particulate solids cannot only clog the wellbore thereby limiting or completely stopping fluid production, they represent a significant wear factor in well production equipment including pumps and seals used in the recovery process. Finally, these particulate solids must be separated from the valuable fluids adding further expense to the processing of these fluids for use.
Particulates which are available for transport in fluids flowing to the wellbore may be present due to an unconsolidated nature of the subterranean formation and/or as a result of various well treatments placing particulate solids into the formation or the near wellbore area such as by fracturing and gravel packing.
Several means have been attempted in order to limit or eliminate flowback of particulate proppant materials placed into the formation in a fracturing process. One means showing reasonable effectiveness has been to gradually release fracturing pressure once the fracturing operation has been completed so that fracture closure pressure acting against the proppant builds gradually allowing proppant matrix to stabilize before fracturing fluid flowback and well production can carry significant quantities of the proppant out of the fractures and back to the wellbore. It has also been common to use so-called "resin-coated proppant" that is particulate proppant materials having an adherent coating bonded to its outer surface so that the proppant particles are bonded to each other, a process which further reduces the possibility of proppant flowback. Since fracturing treatments may employ thousands or even millions of pounds of proppant, the use of expensive, resin-coated proppants is generally limited to use in the final stages of a fracturing treatment for economic purposes.
In unconsolidated formations, it is common to place a filtration bed of gravel in the near-wellbore area in order to present a physical barrier to the transport of unconsolidated formation fines with the production of wellbore fluids. Typically, such so-called "gravel packing operations" involve the pumping and placement of a quantity of gravel and/or sand having a mesh size between 10 and 60 U.S. Standard Sieve Series mesh into the unconsolidated formation adjacent to the wellbore. It is sometimes also desirable to bind the gravel particles together in order to form a porous matrix through which formation fluids can pass while straining out and retaining the bulk of the unconsolidated sand and/or fines transported to the near wellbore area by the formation fluids. The gravel particles may constitute a resin-coated gravel which is either pre-cured or can be cured by an overflush of a chemical binding agent once the gravel is in place. It has also been known to add various binding agents directly to an overflush of uncoated gravel particles in order to bind them together to form the porous matrix.
It has been known in the past to utilize fibrous materials in well treatment fluids in order to prevent or limit fluid loss into a porous formation or vugular zone. In this regard, glass, asbestos, cotton or cellulosic fibers have been pumped in a slurry into a wellbore or formation in order to create a mat of fibrous material over areas of high fluid loss. As the mat builds, flow of well treatment fluids into these high fluid loss areas is inhibited or prevented. Such fluid loss agents are typically pumped in conjunction with drilling fluids or in nonproppant carrying pad solutions preceding a fracturing fluid. The primary intent of using such fibrous materials in these fluids is for arresting or inhibiting fluid flow of fluids in certain desired areas of the wellbore or formation.